Life history reconstructions of Delta Smelt

Delta Smelt (Hypomesus transpacificus) exhibit a life history strategy termed partial migration, which consists of migratory, fresh-water resident, and brackish-water phenotypes. These diverse life-history strategies allow Delta Smelt to persist in the dynamic habitat of the Delta by spreading the risk of catastrophic mortality between multiple habitats. Generally, high freshwater outflow years provide positive benefits for many estuarine species, including Delta Smelt. However, not all high outflow years (e.g., 2006) produce higher abundance for Delta Smelt, indicating that other factors may be limiting abundance and complicating predictions of the effects of fresh water outflow management.
Otoliths (ear bones) provide a life-long archive of physiological (growth) and environmental conditions (chemistry) that a fish has experienced and thus can be used to reconstruct complex life history patterns.